You need to file by mail if you can't get his SSN.
Per IRS : A spouse who is Married Filing Separately is not required to provide the Social Security card for the other spouse, although the return cannot be e-filed without the spouse’s Social Security number.
However, you might be considered unmarried even if you are not divorced or legally separated and, qualify as Head of household.
Married taxpayers may be “considered unmarried” and file as Head of Household if they:
• File a return for the tax year separate from their spouse.
• Paid more than half the cost of keeping up their home. See the Worksheet for Cost of Keeping Up a Home in the Volunteer Resource Guide.
• Lived apart from their spouse during the entire last six months of the tax year. The spouse is considered to have lived in the home even if temporarily absent due to special circumstances, such as military service or education.
• Provided the main home for more than half the year of a dependent child, stepchild, or foster child placed by an authorized agency. This test is also met if the taxpayer cannot claim the exemption only because the noncustodial parent can claim the child using the rules described in Publication 17.
For more information: irs.gov
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
